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Attached are photos of sub panel I am requested to hook up 2 - 7 1/2 HP 3ph air compressors and air drier.

Panel has not been in use for over 10 years.

Only 2- 20 A 1 phase circuits are being utilized.

The installer used Al 4/0-4/0-2/0 tri plex for 3 ph feeder cable and #4 bare cu for EGC and Neutral. The bare copper is run outside the feeder conduit to a trough above the ceiling, after the trough, there is 2 " EMT running about 75 feet to an electrical room and a 200A transfer switch. Facility was built in 1980 and defaulted to bank. Current owner has owned for about 25 years. I am recommending immediately installing 100 amp fuses in the transfer switch. We know the bare EGC/Neutral will put neutral current on the 2" EMT, I need a powerful worded reason to get them to replace that feeder with correct conductors. Note-a separate part of this building is being utilized as a flour mill, and attached to flour mill is living quarters for the mill manager. This is a large family farm / flour mill. I think I have a powerful argument for the safety and investments of the mill and living facility and family members. to get them to replace this feeder. The air compressors are for pneumatic packageing equipment.

The pics are so small that I cannot see any detail and can't seem to blow them up. I am not sure what it is you are asking, but i am interested. It sounds like there are a number of violations in the current installation. Are you asking for advice on how to present an argument for why you could not do what they are asking without first correcting those violations or are you trying to work around them?

Thank you for input petersonra and richwaskowitz. I am reposting pictures.

I am just figureing out how to post images. Hopefully these can be enlarged

Yes I want a strong argument for why this feeder "as is" is a safty concern for personnel and equipment. The NEC violations are obvious. To me the undersized "B" phase is potential fire hazard with 200 amp fuses. While the bare neutral/EGC is major violation, in reallity is it any more dangerous than the millions of 3 prong electric driers and ranges in existence?

Petersora-as constructed, using the EMT for is not an option, because conduit supplying sub panel is PVC. However, when we pull new feeders I will replace it with EMT(it is only about 4' long).

If the Code violations are "obvious" (which a number of are), what more compelling reason to correct the installation are you looking for? Is someone trying to say that they agree that there are violations but that there is no real danger?

If the Code violations are "obvious" (which a number of are), what more compelling reason to correct the installation are you looking for? Is someone trying to say that they agree that there are violations but that there is no real danger?

The point I was trying to make is, why would we start to question aspects of the Code by trying to quantify the risk associated with a particular rule? I may not see the danger in supporting a piece of NM cable at 55 instead of 54 inches between staples, but that is the rule. That is all. Slippery slope and all that stuff.